Grinding mill



Nov. 28, 1933. K. MIDDELBOE 1,937,030

GRINDING MILL Filed June 25, 1931 2 SheetsSheet l 43 I I 1 I I K L I I II anoeuboz /@M @W NOV. 28, 1933. MlDDELBOE 1,937,030

GRINDING MILL Filed June 25, 1931 2 Sheets-Sheet 2 Patented Nov. 28, 1933 1,937,080 H w GRINDING MILL Kristian Middelboe, Frederiksberg near Copen-. hagen, Denmark, assignor to F. L. Smidth 8a- Co -New York, N.- Y., a corporation of- New I a 'Jersey Application June 25, 1931, serial n 54 ,733", and in Great Britain Februaryil, 1931 f 2 Claims. (or sa -45) This invention 'relatesto. the fine grinding of coal, pigments, raw materials for themanufacture of cement, cement-clinker, and .the like, in high-speed mills in which the material is ground by rolling and crushing between rotating grinding surfaces, the grinding bodies, suchas largeballs, cylinders, or other solids of revolution being pressed by centrifugal or other force against. the inner surface of an enclosing grinding-ring,

l0 which may be either rotary or stationary, while the grinding bodies are caused to revolve.

In. the operation of mills of this kind the contact surfaces of the grinding bodies and ofthe grinding ring, wear unevenly and lose true sphericity or cylindricity because the hardness and'wear resistanceofythe contact surfaces are never quite uniform at all points. This leads to the development of shocks and vibrations, the effect of which is multiplied by reason of the load of'the grinding bodies, and consequently ing bodies, by which a smooth running of the mill is ensured. The distances between the grinding bodies are preferably made different, and when the grinding bodies are coupled to- 135. gether in pairs only, the rigid connection between the two grinding bodies of a pair is effected in such a manner that neither of the said bodies can move at right angles to a plane which passes through their points of contact with the grind- ..40 ing ring and is parallel to a plane through their axes of rotation. As a result of these arrangements, irregularities in the grinding surfaces are not exposed to the heavy shocks which would be exerted by a single freely movable grinding body. The coupling of the grinding bodies together in the manner described reduces the pressure of each upon incipient depressions in the grinding surfaces, while the pressure is increased correspondingly on hard and projecting points.

The grinding bodies may contact with the inner, concave grinding surface of an enclosing grinding ring as heretofore, but the invention contemplates also a relative arrangement of 5 grinding ring and grinding bodies such that the grinding bodies work against the outer, convex surface of the grinding r g rather than the inner concave surface. .1 1

In the grinding of moistgand sticky material the tendency of the grinding surface of the grinding ring to be coated-withsuch material, witha Q0 resultant reduced grinding effici ency, is diminishedg; 1 x The invention will now be described with ref erence to the accompanying drawings, wherein:,-

Figures 1 and 2 are views ,in vertical'and-hori: zontal section of a grinding mill which embodies the presentinvention, and I q Figure 3 is aview in horizontal section-ofa modified form of construction. i

As will be seen in Figures 1 and 2, the 7 0;

provided with a casing 1 within which the grind; ing ,is' effectedby a rolling or crushing, action 5 between rotating grinding surfaces. Inthis particular case, these grinding surfaces are formed by a grinding ring 2 which rotates about the ver- 7g, I

tical axis of the mill and provides an outer convex grinding surface, and by six cylindrical grinding bodies 3. The grinding ring is supported by a shaft 4 driven through gearing, 5. The grinding bodies 3 are secured to vertical shafts 6, each of which issuspended in a collar-thrustbearing 7 and is guided below by a bearing 8. Both of these bearings are carried bya common housing 9. The housings are rigidly connected together in pairs, that is, at fixed distances apart 8;

and without freedom for relative movement about a vertical axis by frames 9 and at the upper end are suspended so as' to swing on a horizontal axis by pivots 10 in bearings outside the casing. By thismethod of suspension and coupling to- 99; gether of the grinding bodies in pairs, the individual grindingbodies are prevented from moving independently of each other at right angles to a plane which passes through their points of contact with the grinding ring and is parallel to their axes of rotation. The grinding bodies of 1 each set are together pressed against the grinding ring by means of springs 11 which may be connected at their ends to lugs 9 of adjacent frames 9 A smooth running of the mill may be further ensured by making unequal the distances between the grinding bodiesv of different I pairs so that the coupled grinding bodies do not readily form corresponding depressions in the grinding surface of the ring 2. t 1499 The material to be ground is supplied to the mill through chutes .12 arranged in'a circle, by which the material is led down directly in front of each grinding body 3, in such a. manner that the material is immediately caught and crushed up ing surfaces. When the material has passed between the grinding ring and the grinding bodies, it is caught at the bottom of the casing by blades 16 secured to the shaft 4, by which it is projected outwardly through a dischargepipe 1'7. At this. stage, fines of the material being groundma'y be separated and carried off while the coarser'particles may be returned to the mill.

Figure 3, in which similar reference characters indicate corresponding parts, shows a rigid inter-coupling of the grinding bodies inthreesn The above described pivotal suspension of the supporting frames is not so necessary in this case for vpreventing the individual grinding bodies from increasing incipient unevenness in the grinding surfaces, as two ofthe grinding bodies will prevent the third frommoving freely and independently against the grinding ring.

It will; be noted that each supporting frame composed of the housings 9 and the connecting frame 9 and. the bearings, is rigid in itself and is movable as a unit toward the grinding 'ring under the influenceof the springs 11, without movement of oscillation about a vertical axis,-that the grinding bodies of each set are supported on fixed axes in the frame at fixed distances apart, although the distance between the grinding bodies of each set may be different from thedistance between the gri'nding bodies of ':every other set, and that each frame and'the'grindin'gbodies supported by it are pressed toward the grinding ring as a unit independently of each other frame. In this manner when one of the rollers of a set bears against the grinding ring the other roller or rollers of that set are prevented fromentering any incipientrecess in the grinding ring. i

It will be seen that the coupled grinding bodies might be arranged to bear against the inner, concave surface of an encompassing grinding ring and that other changes might be madeto suit different conditions of use, the invention-not being restrictedto any particular construction, ex-

cept aspointed out in the accompanying claims.

- I-claimas my invention:

1. In a grinding mill,'the combination of a grinding ring, a plurality of rigid supporting frames, each'fr'amebeingmovable as a unit toward and from the grinding ring without movement about a vertical axis, a plurality of grinding bodies supported on fixed axes in each frame at a fixed distance apartgand means'to press each frame and the grinding :zbodies supported by it'as a unit together toward the grinding ring. "2. In a grinding mill, the combination of a grinding :ring, a plurality of Hrig'idtsupporting 

